Polychaete assemblages in the San Jose Gulf (Chubut, Argentina), in relation to abiotic and biotic factors

Abstract

The composition and distribution of the polychaete assemblages of the San Jose Gulf (Chubut, Argentina) are described in relation to environmental variables using indicator species (TWINSPAN) and canonical correspondence analysis (CCA). The polychaetes were collected during a benthic cruise in October 1984. Sediments were collected at 110 sampling sites using a 0.25 m2 van Veen bottom grab or by divers in near-shore areas and sieved with 1 mm mesh. A total of 73 polychaete taxa were collected and identified. Both analyses revealed the presence of four main assemblages distributed according to depth as well as bivalve and seaweed abundance gradients: 'Syllis-Eunice' and 'Harmothoe-Eunice' assemblages occurred at the same depths (0-185 m) and substrata (poorly sorted rock and coarse sand), but were separated by bivalve and seaweed abundance, wherby the highest abundances of bivalves and the minimum abundances of seaweeds corresponded to the 'Syllis-Eunice' association. The 'Ninoe-Glycera' and 'Aglaophamus-Fabriciinae indet. 6′ assemblages also occurred at similar depths (0-60 m) and substrata (very well-sorted medium-fine sand), but differed in their composition of bivalves and seaweed abundances; the 'Aglaophamus-Fabriciinae indet. 6' association corresponded with minimum bivalve and maximum seaweed abundances.